Ok, in that case I'd try using your 5.1 Ipsw & create a custom firmware (preserve baseband) & try to update it that way in DFU mode & see if this still causes you an issue. Did you use a program to get it out of recovery mode?

Error 11 is usually caused by a missing BB from the FW.
As your device is not JB and is factory unlocked the first thing to do is confirm the ipsw is 720,402,781 bytes - if it is then it should be OK so just putting your phone in DFU and restoring that file should work.

He who asks a question looks foolish for 5 minutes. He who doesn't ask a question remains foolish forever.

The file size seems correct ( just rounded up to th next highest kb)
Your Apple redirection to cydia is commented out, so that's fine.
Now just put your phone in DFU mode and restore it and all will be fine.

He who asks a question looks foolish for 5 minutes. He who doesn't ask a question remains foolish forever.